Fade background when general text field dialog is opened.

Fixes #3240

src/states_screens/dialogs/general_text_field_dialog.cpp

@@ -37,7 +37,6 @@ GeneralTextFieldDialog::GeneralTextFieldDialog(const wchar_t* title,
                     GUIEngine::MODAL_DIALOG_LOCATION_BOTTOM),
                     m_dm_cb(dm_cb), m_val_cb(val_cb), m_self_destroy(false)
 {
-    m_fade_background = false;
     loadFromFile("general_text_field_dialog.stkgui");
 
     m_text_field = getWidget<TextBoxWidget>("textfield");